1. Field of the Invention
The invention relates to a floating LNG plant comprising a first and a second converted LNG carrier each provided with a hull and at least one LNG storage tank wherein the floating LNG plant further comprises a connection structure for connecting the hull of the first and the second converted LNG carrier in order to obtain a catamaran type or so called “twin-hull” vessel, process equipment for LNG processing on the floating LNG plant, and a mooring system for mooring the floating LNG plant on the seabed.
The floating LNG plant according to the present invention is specifically suitable to be used as an LNG floating production, storage and offloading unit (LNG FPSO).
2. Description of the Related Art
A FPSO is a floating vessel used in the offshore industry for the processing and storage of hydrocarbons such as oil and gas. A FPSO vessel is designed to receive hydrocarbons produced from a nearby plant or a subsea template. The vessel is adapted to process on board the hydrocarbons, to store the hydrocarbons until the hydrocarbons can be offloaded onto a tanker or transported towards an on-shore facility by means of a pipeline.
An FPSO can specifically be built for its final application (new build FPSO). Alternatively, an FPSO can be obtained by conversion of an existing vessel. The advantage of such a FPSO obtained by conversion, is that using an existing structure reduces project risks because of the fact that the existing vessel is readily available and construction of the complete vessel hull not on the critical path. Moreover, project schedules can be reduced to the delivery time of the topsides only. Additionally, the overall scale of the project and the related costs for obtaining the FPSO is significantly reduced compared with the scale and costs of newly build FPSO's.
In the prior art several solutions for converting existing vessels in order to obtained a FPSO have been described.
The international patent application WO2010059059 discloses a device for floating production of LNG and a method for converting an LNG-carrier to a floating device for LNG production. According to WO2010059059 the existing LNG-carrier is provided with an additional projecting hull structure which is fixed to the outside of the ship hull. Once the projecting hull structure is provided, the equipment for the LNG production is arranged in this projecting hull structure. That means that according to WO2010059059 the additional internal space created by adding the projecting hull structure is used to contain at least part of the gas liquefaction process equipment.
An important disadvantage of the solution according to WO2010059059 is the fact that gas process equipment is contained in an enclosed space, which can potentially lead to very dangerous situations because of the risk of an explosion in an enclosed space due to leakage of gas from the gas process equipment. The solution according to WO2010059059 will increase the volume of space available for process equipment. However, the additional structure provided does not increase the weight carrying capacity and stability of the vessel.
Another disadvantage is linked to the fact that according to the solution of WO2010059059 the gas liquefaction process equipment is installed in the space created at the side of the hull, which leads to a dangerous configuration in view of possible side collisions, with for example a shuttle tanker. Such side collisions would directly damage the gas process equipment in the projecting hull structures.